In many ink jet printers, sealed ink jet cartridges containing a fixed supply of ink are utilized. The cartridges are passed over the paper, and ink is ejected from the cartridge to form the image. When the ink in a particular cartridge has been depleted, the cartridge is replaced. To maximize printhead use, some printers incorporate separate stationary large volume ink supplies, and the ink in these supplies is routed via tubing from the external supply to the print cartridges. Examples of systems of this type are described in U.S. Pat. Nos. 5,686,947 and 6,637,864. The disclosures of these patents are hereby incorporated by reference in its entirety.
Print quality is highly dependent on accurate ink droplet placement on the media. Accordingly, any deviations in printhead position during printing (other than the desired printhead scanning motion across the media) can result in inaccurate drop placement and/or size, and thus reduce image quality.
One source of printhead position variation can arise from the ink supply tubing that is connected to the moving carriage that holds the ink jet cartridges. External forces from the ink supply tubing can be transmitted to the carriage, causing vibrations and other positional deviations of the cartridges as they pass over the media. In some printer embodiments, the weight of the ink supply tubing that is supported by the carriage varies with carriage position from one side of the printer to the other. In these cases, the carriage can be forced to rock backward and forward around its support shaft as the weight of the tubing increases and decreases during passes over the media. Since this positional deviation is consistent with carriage location during a scan, print errors caused by this problem appear as visible vertical banding in the printed image.
Currently, printhead carrier assemblies for printers have bushings that run on two shafts or bushings that run on a single shaft with sliders that prevent rotation of the assembly and possibly a subassembly running on a surface. In current designs, the slider is made from a low friction material, such as plastic in order to minimize friction.
Previous printers have attempted solve the vibration problem by using a plastic slider. The plastic slider is not an ideal solution because the slider is susceptible to defects on the surface of the part the slider is sliding against.